Methods and apparatus to verify presentation of media content

ABSTRACT

Example methods and apparatus to verify presentation of media content are disclosed. A disclosed example apparatus for use with a set-top box (STB) and a media presentation device includes an audio input interface to receive a first audio signal associated with a program selected by a user via the STB, a microphone to receive a free-field radiating second audio signal output by at least one of the media presentation device or an audio system associated with the media presentation device, a comparator to compare the second audio signal to the first audio signal to form an output, and an output interface to provide a value indicative of whether the program selected by the user via the STB is presented at the media presentation device.

RELATED APPLICATIONS

This patents claims the benefit of U.S. Provisional Patent ApplicationNo. 61/110,274, entitled “Methods and Apparatus to Monitor MediaContent,” and filed Oct. 31, 2008, which is hereby incorporated byreference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to media content and, moreparticularly, to methods and apparatus to verify presentation of mediacontent.

BACKGROUND

In audience measurement applications, determining the media contentbeing presented by a media presentation device (e.g., a televisionprogram being displayed on a television) can be accomplished by, forexample, monitoring the audio emanating from the media presentationdevice. If the presented media content includes watermarks, codes, orother identifiers embedded in the content, then extracting theidentifier(s) facilitates the detection of program information. Analternative to this “active” approach is a “passive” technique based oncomputed fingerprints or signatures. Signatures are unique orsemi-unique representations of media content segments derived from oneor more of the properties of the media content signal, such as its localfrequency distribution. Signature methods require reference signaturesfor all possible media content of interest. By comparing signaturesderived from media content presented by a media presentation device(e.g., a home television set) with the reference signatures, the mediacontent (e.g., a television program) being presented by the mediapresentation device can be identified.

Persons subscribing to cable, Internet protocol (IP), wireless and/orsatellite content distribution services often receive media contentsignals via, for example, a set top-box (STB) installed by a serviceprovider and/or a user. An example STB can determine, log and/or reportinformation about media content (e.g., channels) tuned to and/orselected via user controls, such as a remote control. This media contentinformation may be transmitted back to the service provider and/or anaudience measurement entity via a back channel. By analyzing suchinformation from one or more customer premises, ratings informationand/or media consumption statistics can be determined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example home entertainment system.

FIG. 2 is a block diagram of an example media content delivery systemincluding a presentation verifier constructed in accordance with theteachings of this disclosure.

FIG. 3 illustrates an example manner of implementing the examplepresentation verifier and/or, more generally, the example STB of FIG. 2.

FIG. 4 illustrates an example standalone in-line presentationverification device that may be used to implement the examplepresentation verifier of FIG. 2.

FIG. 5 illustrates an example manner of implementing the examplecomparators of FIGS. 3 and 4.

FIG. 6 illustrates an example filter coefficient magnitude distribution.

FIG. 7 is a flowchart representative of example machine-accessibleinstructions that may be executed by, for example, a processor toimplement the example presentation verifiers of FIGS. 2, 3 and/or 4.

FIG. 8 is a flowchart representative of example machine-accessibleinstructions that may be executed by, for example, a processor toimplement the example metering module of FIGS. 2 and 3.

FIG. 9 is a block diagram of an example processor platform that may beused and/or programmed to carry out the example machine-accessibleinstructions of FIGS. 7 and 8, and/or to implement the example methodsand apparatus to verify media content presentation described herein.

DESCRIPTION

Example methods and apparatus to verify presentation of media contentare disclosed. A disclosed example apparatus for use with a set-top box(STB) and a media presentation device includes an audio input interfaceto receive a first audio signal associated with a program selected by auser via the STB, a microphone to receive a free-field radiating secondaudio signal output by at least one of the media presentation device oran audio system associated with the media presentation device, acomparator to compare the second audio signal to the first audio signalto form an output, and an output interface to provide a value indicativeof whether the program selected by the user via the STB is presented atthe media presentation device.

Another disclosed example apparatus for use with a STB and a mediapresentation device a transducer to receive a free-field radiating firstaudio signal output by at least one of the media presentation device oran audio system associated with the media presentation device, a filterhaving adaptive weights to receive a second audio signal associated witha program selected by a user from an audio output line of the STB, andto process the second audio signal to generate a delayed and attenuatedthird audio signal, a difference detector to subtract the third audiosignal from the first audio signal to form a residual signal, and acomparator to form a value indicative of whether the program selected bythe user via the STB is presented at the media presentation device.

A disclosed example method to verify presentation at a mediapresentation device of media content selected at a tuning deviceincludes receiving a first audio signal associated with the mediacontent received at the tuning device, receiving a free-field radiatingsecond audio signal output by the media presentation device, comparingthe second audio signal to the first audio signal to form an output, andproviding a value indicative of whether the media content received bythe tuning device was presented at the media presentation device.

FIG. 1 is a block diagram of an example prior-art home entertainmentsystem 100 that includes a STB 102, a digital versatile disk (DVD)player 104, a video game console 106, and a television 108. While a usermay turn on the example STB 102 and select a particular media contentchannel and/or program, the television 108 may be set to displaydifferent media content output by the DVD player 104 and/or the videogame console 106. Thus, even when the STB 102 is configured to tuneand/or to receive a specific channel and/or media content, there is noguarantee that the television 108 connected to the STB 102 is set toactually use the STB 102 as its input source. Accordingly, the exampleSTB 102 of FIG. 1 cannot determine and/or verify whether the television108 is actually presenting the media content output by the STB 102.

FIG. 2 illustrates an example media content delivery system 200 thatincludes a presentation verifier 205 to verify the presentation of mediacontent by and/or at any number and/or type(s) of media presentationdevices, one of which is designated at reference numeral 210. While fordiscussion purposes, the example media presentation device 210 of FIG. 2is a television, the methods and apparatus described herein may be usedto verify media content presentation by and/or at any other numberand/or type(s) of media presentation devices. As described below inconnection with FIGS. 3 and 4, the example presentation verifier 205 ofFIG. 2 can be implemented by and/or within a tuning device 215, such asa STB, and/or may be implemented as a standalone device 400 (FIG. 4)placed and/or installed in-line between the example STB 215 and theexample television 210. Moreover, while a STB is depicted in FIG. 2, anyother number and/or type(s) of devices (e.g., a personal computer, agame console, a smart phone, a cellular phone, etc.) may, additionallyor alternatively, be used to implement the tuning device 215.

Media content (e.g., television programs, movies, radio programs,videos, games, audio, etc.) may be provided to the STB 215 by any numberand/or type(s) of service providers, four of which are designated atreference numerals 220, 221, 222 and 223. Example service providers220-223 include, but are not limited to, a cable television basedservice provider 220, a cellular and/or wireless based service provider221, a satellite based service provider 222, and/or an Internet protocol(IP) television (IPTV) based service provider 223. Media contentreceived at the STB 215 may be encoded and/or formatted in accordancewith any past, present and/or future standard, specification, formatand/or recommendation, such as a National Television Standards Committee(NTSC) television signal format, a high definition television (HDTV)signal format, an Advanced Television Systems Committee (ATSC)television signal format, a phase alteration line (PAL) televisionsignal format, a digital video broadcasting (DVB) television signalformat, an Association of Radio Industries and Businesses (ARIB)television signal format, etc. Moreover, the example STB 215 of FIG. 2may be communicatively coupled to the example service providers 220-223via any number and/or type(s) of communication path(s), medium(s) and/orcommunication device(s). For example, the IPTV based service provider223 may be communicatively coupled to the STB 215 via any public and/orprivate IP-based network, such as the Internet 225. The examplecellular, wireless and/or satellite based service providers 221 and 222may be communicatively coupled to the STB 215 via an antenna 230.

In the illustrated example of FIG. 2, the television 210 is located in aviewing area 235 within a customer premises occupied by one or morepersons (also referred to herein as household member(s) 240), at leastsome of whom have agreed to participate in an audience measurementresearch study. The example viewing area 235 of FIG. 2 includes the areain which the television 210 is located and from which the television 210may be viewed by the household member(s) 240 present in the viewing area235.

To collect media content consumption, presentation and/or viewinginformation with respect to the household member(s) 240, the example STB215 of FIG. 2 includes a metering module 245. The example meteringmodule 245 of FIG. 2 provides collected media viewing, presentationand/or consumption information, as well as other tuning and/ordemographic data, via, for example, the Internet 225 to a central datacollection facility 280. The example data collection facility 280 ofFIG. 2 processes and/or stores data received from the metering module245, and/or similar devices in other viewing areas and/or at othercustomer premises, to produce ratings information and/or to developmeaningful content exposure statistics. For instance, the example datacollection facility 280 can determine the overall effectiveness, reachand/or audience demographics of media content using any number and/ortype(s) of statistical method(s). In some examples, the metering module245 stores a log of audience measurement data and periodically (e.g.,once a day) and/or aperiodically (e.g., upon occurrence of one or moreevents and/or conditions) sends the collected data to the datacollection facility 280 for processing. Additionally or alternativelyinformation associated with the presented media content and thehousehold member(s) 240 may be provided to the data collection facility280 in real-time or substantially real-time as the presentation of mediacontent occurs.

The example metering module 245 of FIG. 2 interacts with any numberand/or type(s) of tuners 305 (FIG. 3) implemented by and/or within theSTB 215 to identify which media content is and/or has been receivedand/or tuned by the STB 215. Additionally or alternatively, the audiencemetering module 245 can identify the tuned and/or received media contentfrom watermarks that have been embedded in the media content (e.g., anyaudio or video watermark) and/or based on computed and/or derivedsignatures (e.g., audio signatures, video signatures, etc.). However, asdescribed above, such media content may not actually be presented by thetelevision 210 even though tuned, received and/or output by the STB 215.For example, when the STB 215 is operating but the person 240 is playinga computer game via the television 210, media content received, tunedand/or output by the STB 215 is not actually presented to the person 240and, thus, should not be recorded, logged and/or reported by themetering module 245 as having been presented.

To verify media content presentation, the example presentation verifier205 of FIG. 2 compares audio data X_(c) output and/or provided by theexample STB 215 to the example television 210 with a free-fieldradiating audio signal 255 output by a speaker of the television 210and/or by an audio system associated with the television 210. When theexample presentation verifier 205 determines that the audio data X_(c)output by the STB 215 substantially and/or sufficiently corresponds tothe audio signal 255 presented by the audio equipment associated withthe television 210, then the metering module 245 logs and/or reports thetuned and/or received media content as presented by the television 210.By verifying the presentation of media content, the accuracy of theaudience measurement information reported and/or stored by the meteringmodule 245 is improved and, accordingly, ratings information developedby the data collection facility 280 are more accurate and/orrepresentative of actual audience behavior.

While the example components shown in FIG. 2 are depicted as separatestructures within the media content delivery system 200, the functionsperformed by these components may be integrated within a single unit ormay be implemented as two or more separate components. For example,although the television 210 and the STB 215 are depicted as separatedevices, the television 210 and the STB 215 may be implemented in asingle unit. In other examples, the STB 215, the metering module 245 andthe presentation verifier 205 may be implemented as physically separatedevices communicatively coupled via one or more cables. In still otherexamples, the television 210, the STB 215, the metering module 245, andthe presentation verifier 205 are implemented in a single unit.

FIG. 3 illustrates an example manner of implementing the examplepresentation verifier 205 and/or, more generally, the example STB 215 ofFIG. 2. In the example of FIG. 3, the tuner 305, the metering module 245and the presentation verifier 205 are implemented in, by and/or togetherwith the STB 215. The example tuner 305 of FIG. 3 receives media contentsignals from one or more of the example service providers 220-223 ofFIG. 2. Based on user inputs, the example tuner 305 tunes to and/orotherwise obtains media content selected by a user of the STB 215, andoutputs corresponding audio and/or video portions of the media contentto the attached media content presentation device 210. As illustrated inFIG. 3, the audio portion of the media content is also provided to acomparator 325.

To receive the free-field radiating audio signal 255 output by a speakerof the example television 210 and/or by an audio system associated withthe television 210, the example presentation verifier 205 of FIG. 3includes any type of microphone 310 (e.g., a transducer), any type ofpre-amplifier 315 and any type of analog-to-digital converter (ADC) 320.The example microphone 310 of FIG. 3 converts the free-field radiatingsound waves 255 into an electrical signal that is amplified by theexample pre-amplifier 315 and converted to a stream of digital samplesX_(d) by the example ADC 320. In some examples, the microphone 310 isaffixed to a side of the STB 215 and picks up audio 255 in the vicinityof the STB 215. Additionally or alternatively, the microphone 310 may bewired or wirelessly coupled to the STB 215 so that the microphone 310can be placed in a desired location separate from the STB 215. Inaddition, the microphone 310 may be replaced by any other type of audioinput. For example, the STB 215 may be attached to an audio output ofthe media presentation device 210, and/or a speaker and/or speaker wireof the media presentation device 210 or an audio system associated withthe media presentation device 210. While not shown in FIG. 3, if theaudio signal X_(c) output by the tuner 305 is an analog signal, theaudio signal X_(c) is also converted to a stream of digital samplesusing an amplifier and ADC similar to the pre-amp 315 and the ADC 320,respectively. Accordingly, during the following discussion, X_(c) willbe used to refer to a stream of digital samples corresponding to theaudio output by the tuner 305.

To compare the audio signal X_(c) output by the tuner 305 to the digitalrepresentation X_(d) of the audio signal 255 output by the television210 and/or an audio system associated with the television 210, theexample presentation verifier 205 of FIG. 3 includes the comparator 325.The example comparator 325 of FIG. 3 compares the two audio signalsX_(d) and X_(c) to determine whether they have similarities. The examplecomparator 325 determines whether the audio signal X_(c) received fromthe tuner 305 is present, albeit in a possibly modified form, in theaudio signal X_(d) received via the microphone 310. In other words, thecomparator 325 determines whether the media content presentation device210 attached to the STB 215 is presenting the media content tuned toand/or received via the STB 215 so that the audio signal X_(c)associated with the media content is present in the ambient audio 255 atthe location of the media content presentation device 210.

To compare the audio signals X_(c) and X_(d), the example comparator 325of FIG. 3 applies a filter 505 (FIG. 5), which compensates for delayand/or attenuation present between audio signal X_(c) and the audiosignal X_(d). When the coefficients of the filter 505 have been adaptedto represent such delay and/or attenuation characteristics, the filteredaudio signal X_(c) will substantially match the audio signal X_(d). Howclosely the filtered audio signal X_(c) and the audio signal X_(d) matchcan be determined by, for example, subtracting the filtered audio signalX_(c) from the audio signal X_(d) to form a residual signal. When theyare substantially similar, the residual signal will have a smallmagnitude and/or small signal strength. Thus, by comparing the magnitudeof the residual signal to a threshold, the example comparator 325 ofFIG. 3 can determine whether the media content received and/or tuned bythe tuner 305 was presented at the media presentation device 210.Additionally or alternatively, as described below in connection withFIG. 6, the coefficients of the filter 505 can be analyzed to determinewhether the media content was presented. An example filter structure,commonly referred to in the industry as an echo canceller, that can beused to implement the example comparator 325 is described below inconnection with FIG. 5.

When the example comparator 325 of FIG. 3 determines that the signalsX_(d) and X_(c) correspond to the same media content (e.g., when theresidual signal of the comparator 325 has a small magnitude), theexample comparator 325 provides an indication 330 having a first value(e.g., TRUE or one) to the metering module 245 that the media contentreceived and/or tuned via the tuner 305 was presented by and/or at themedia presentation device 210. Otherwise, the example comparator 325outputs the indication 330 having a second value (e.g., FALSE or zero)to the metering module 245 that the media content received and/or tunedvia the tuner 305 was not presented by and/or at the media presentationdevice 210.

Based on the indication 330, the example metering module 245 determineswhether media presentation information for the media contentcorresponding to the audio signal X_(c) should be stored and/or providedto the data collection facility 280. The example metering module 245 mayadditionally store and/or transmit to the data collection facility 280additional information about the currently tuned program. For example,the metering module 245 and/or the tuner 305 may extract metadata fromthe media content provider signal and/or metadata in a program guide andtransmit the information together with an identification as to whetheror not the media content presentation device 210 presented the mediacontent. Accordingly, the STB 215 and/or the data collection facility280 can determine what media content was tuned by the STB 215 andwhether that media content was presented by the media contentpresentation device 210 attached to the STB 215. The STB 215 mayassociate the identification with a timestamp so that the informationtransmitted to the data collection facility 280 can be used to determinethe time(s) that the media content was presented by the media contentpresentation device 210.

To protect the privacy of the household member(s) 240, the examplepresentation verifier 205 of FIG. 3 includes a timer 335. The exampletimer 335 periodically and/or aperiodically enables and disables themicrophone 310, the pre-amp 315 and/or the ADC 320 such that thecomparator 325 and/or, more generally, the example presentation verifier205 operate in a burst mode. For example, the timer 335 may enable themicrophone 310, for example, for three seconds to allow the comparator325 to converge its filter coefficients and to make a determinationwhether the audio signal X_(d) corresponds to the audio signal X_(c).The timer 335 may then disable the microphone 310 for several seconds,before re-enabling the microphone 310. How often the microphone 310 isenabled may be selected based on a desired granularity of media contentpresentation information to be reported by the example metering module245.

FIG. 4 illustrates an example manner of implementing the examplepresentation verifier 205 of FIGS. 2 and 3 as a standalone in-linepresentation verification device 400 that is user installable betweenthe STB 215 and the television 210. That is, the example in-linepresentation verification device 400 of FIG. 4 can be installed betweenthe STB 215 and the television 210 at a time other than (e.g., after)when either the STB 215 or the television 210 were manufactured and/orassembled. Some components of the example in-line presentationverification device 400 of FIG. 4 are substantially similar or identicalto those of FIG. 3. Accordingly, identical references numerals have beenused in FIGS. 3 and 4 for identical components, and the interestedreader is referred to the discussion presented above in connection withFIG. 3 for descriptions of the identically numbered components.

To allow the in-line presentation verification device 400 to be userand/or technician installed between the STB 215 and the mediapresentation device 210, the example in-line presentation verificationdevice 400 of FIG. 4 includes connectors C1, C2 and C3. The exampleconnector C1 of FIG. 1 is to electrically couple the audio signal X_(c)from an audio-out jack and/or connector of the STB 215 to the comparator325 via a first cable. As shown in FIG. 4, the audio signal X_(c)received via the connector C1 is also passed through and output via theexample connector C2. The example connector C2 of FIG. 4 is toelectrically couple the audio signal X_(c) to an audio-in jack and/orconnector of the media presentation device 210 via a second cable. Asillustrated in FIG. 4, the in-line presentation verification device 400of FIG. 4 may be installed in-line between the audio-out jack of the STB215 and the audio-in jack of the media presentation device 210. Exampleconnectors that may be used to implement the connectors C1 and C2include, but are not limited to, an RCA connector, an high-definitionmultimedia interface (HDMI) connector, a tip-sleeve (TS) connectorand/or a tip-ring-sleeve (TRS) connector.

The media content presentation verification indications 330 determinedby the comparator 325 are provided to the metering module 245 via theexample connector C3. In some examples, the example connector C3 of FIG.4 is a universal serial bus (USB) connector and a USB protocol and/ordata signal is used to transfer the indication 330 from the comparator325 to the metering module 245 and/or, more generally, to the exampleSTB 215.

While example manners of implementing the example presentation verifier205 of FIG. 2 have been illustrated in FIGS. 3 and 4, one or more of theinterfaces, data structures, elements, processes and/or devicesillustrated in FIGS. 3 and/or 4 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample tuner 305, the example metering module 245, the examplepresentation verifier 205, the example microphone 310, the examplepre-amp 315, the example ADC 320, the example comparator 325, theexample timer 335 and/or, more generally, the example STB 215 and theexample in-line presentation verification device 400 of FIGS. 3 and 4,respectively, may be implemented by hardware, software, firmware and/orany combination of hardware, software and/or firmware. Thus, forexample, any of the example tuner 305, the example metering module 245,the example presentation verifier 205, the example microphone 310, theexample pre-amp 315, the example ADC 320, the example comparator 325,the example timer 335 and/or, more generally, the example STB 215 andthe example in-line presentation verification device 400 may beimplemented by one or more circuit(s), programmable processor(s),application-specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)), field-programmable logic device(s) (FPLD(s)), and/orfield-programmable gate array(s) (FPGA(s)), etc. When any claim of thispatent incorporating one or more of these elements is read to cover apurely software and/or firmware implementation, at least one of theexample tuner 305, the example metering module 245, the examplepresentation verifier 205, the example microphone 310, the examplepre-amp 315, the example ADC 320, the example comparator 325, theexample timer 335 and/or, more generally, the example STB 215 and theexample in-line presentation verification device 400 are herebyexpressly defined to include a tangible computer-readable medium.Example tangible computer-readable media include, but are not limitedto, a flash memory, a compact disc (CD), a DVD, a floppy disk, aread-only memory (ROM), a random-access memory (RAM), a programmable ROM(PROM), an electronically-programmable ROM (EPROM), and/or anelectronically-erasable PROM (EEPROM), an optical storage disk, anoptical storage device, magnetic storage disk, a magnetic storagedevice, and/or any other tangible medium that can be used to storeprogram code and/or instructions in the form of machine-readableinstructions or data structures, and which can be accessed by aprocessor, a computer and/or other machine having a processor, such asthe example processor platform P100 discussed below in connection withFIG. 9. Combinations of the above are also included within the scope oftangible computer-readable media. Further still, the example STB 215and/or the example in-line presentation verification device 400 mayinclude interfaces, data structures, elements, processes and/or devicesinstead of, or in addition to, those illustrated in FIGS. 3 and/or 4,and/or may include more than one of any or all of the illustratedinterfaces, data structures, elements, processes and/or devices.

FIG. 5 illustrates an example manner of implementing the examplecomparator 325 of FIGS. 3 and 4. The example comparator 325 of FIG. 5 isconfigured as an echo canceller. Thus, the example comparator 325operates to modify the audio signal X_(c) that corresponds to the audiosignal X_(d) (if present) so that when the filtered version X_(T) of theaudio signal X_(c) is subtracted from the audio signal X_(d), theresidual signal X₀ is minimized. Accordingly, when the audio signalX_(c) substantially comprises a modified version of the audio signalX_(d), the residual signal X₀ will be small.

To form the estimate X_(T) of the audio signal X_(d) from the receivedaudio signal X_(c), the example comparator 325 of FIG. 5 includes afinite impulse response (FIR) filter 505. To compensate for audiopropagation delays and/or multiple sound wave paths due to reflectionsoff of walls and/or other objects in the viewing area 235, the examplefilter 505 includes a delay line 510 of M shift registers. To compensatefor attenuation of the audio signal 255 during its propagation throughthe viewing area 235, the example filter 505 includes one or more filtercoefficients 515. Filter coefficients may also be referred to as weightsand/or filter taps. To adjust the audio signal X_(c) so that the portionof the audio signal X_(c) corresponds more closely with the audio signalX_(d), the audio signal X_(c) has to be delayed and attenuated, as shownin FIG. 5. In the illustrated example of FIG. 5, the filter coefficient515 with the largest magnitude corresponds to the delay that the audioX_(c) is subjected-to in order to align itself with the microphone 310detected audio signal X_(d). In some examples, the distribution of thefilter coefficients 515 may be configured to ensure that the coefficientwith the maximum magnitude is significantly larger than the othercoefficients. Accordingly, as shown in FIG. 6, the other coefficients515 in the vicinity of the coefficient 515 with the maximum magnitudeexhibit a decay characteristic. For convenience, only the first 200 of400 taps are shown in the graph of FIG. 6. The maximum filtercoefficient magnitude (in this example 0.033) is an indicator of theextent of attenuation that the audio signal X_(c) has experiencedbetween the internal tuner 305 and the microphone 310.

The output X_(T) of the filter 505 is a summation of the weightedsamples, which can be mathematically expressed as:

$\begin{matrix}{{X_{T} = {\sum\limits_{m = 0}^{m = {M - 1}}\;{W_{m}Z_{m}}}},} & {{EQN}\mspace{14mu}(1)}\end{matrix}$where W_(m) are the values of the filter coefficients 515. The valuesX_(m) correspond to the differently delayed samples of the audio signalX_(c) formed by the example delay line 510 of FIG. 5. To compute the sumof the weighted samples, the example comparator 325 of FIG. 5 includesany type of summer 518.

To adapt the filter coefficients 515, the example comparator 325 of FIG.5 includes a coefficient adapter 520. The example coefficient adapter520 adjusts the filter coefficients 515 to minimize the difference X₀between the audio signal X_(d) and the filtered audio signal X_(T). Thatis, the coefficient adapter 520 operates to substantially minimize theresidual signal X₀. In some example, the initial values of the filtercoefficients 515 are set to zero when the microphone 310 is enabled.Additionally or alternatively, the values of the filter coefficients 515can be frozen, fixed and/or retained while the microphone 310 isdisabled. The example coefficient adaptor 520 adjusts the filtercoefficients 515 by applying the following equation:W _(m)(n+1)=W _(m)(n)+μX ₀ X _(m)(n),  EQN (2)where the index n is an iteration index denoting the time in samplecounts at which the coefficient updates are made and μ is a learningfactor, which is usually set to a low value such as 0.05. Theapplication of EQN (2) gradually minimizes the least mean squared (LMS)value of the residual error signal X₀.

To compute the error and/or residual signal X₀, the example comparator325 of FIG. 5 includes a subtractor 525. The example subtractor 525generates the residual signal X₀ by subtracting the filtered signalX_(T) from the audio signal X_(d).

An example implementation uses a 16 kHz sampling rate (any desiredsampling rate may be used) and uses M=400 filter coefficients 515 W₀through W_(M-1), supporting a maximum time delay of 25 millisecondsbetween the audio signal X_(c) and the audio signal X_(d). If the audioX_(d) picked up by the microphone 310 predominantly corresponds to theaudio signal X_(c), the filter weights 515 readily adapt themselves tosubstantially stationery values and the error signal X₀ decreases to alow value in approximately one second. The extent to which the residualsignal X₀ is not zero may depend on any number and/or type(s) offactors, such as the presence of ambient noise in the viewing area 235,quantization noise, computation noise, finite-precision arithmeticeffects, etc. When the audio X_(d) is different from the audio X_(c),the adaptation process will not be able to substantially reduce and/orminimize the error signal X₀. Therefore, by comparing the error signalX₀ energy with a threshold (e.g., a predetermined threshold), thecomparator 325 can determine whether the audio 255 emanating from thespeakers matches the tuner audio X_(c). When a good match is identified,the comparator 325 can also analyze the distribution of filtercoefficients to determine whether one filter coefficient has a magnitudethat is greater than all the other coefficients, as depicted in FIG. 6.

To compare the magnitude of the residual signal X₀ to a threshold, theexample comparator 325 includes a thresholder 530. When the magnitude ofthe residual signal X₀ exceeds the threshold, the indication 330 has afirst value (e.g., TRUE or one). When the magnitude of the residualsignal X₀ does not exceed the threshold, the indication 330 has adifferent value (e.g., FALSE or zero).

While an example manner of implementing the example comparators 325 ofFIGS. 3 and 4 has been illustrated in FIG. 5, one or more of theinterfaces, data structures, elements, processes and/or devicesillustrated in FIG. 5 may be combined, divided, re-arranged, omitted,eliminated and/or implemented in any other way. For example, thesubtractor 525 and the filter 505 may be implemented in the same orseparate integrated circuits. Further, the example filter 505, theexample delay line 510, the example filter coefficients 515, the examplesummer 518, the example coefficient adapter 520, the example subtractor525, the example thresholder 530 and/or, more generally, the examplecomparator 325 of FIG. 5 may be implemented by hardware, software,firmware and/or any combination of hardware, software and/or firmware.Thus, for example, any of the example filter 505, the example delay line510, the example filter coefficients 515, the example summer 518, theexample coefficient adapter 520, the example subtractor 525, the examplethresholder 530 and/or, more generally, the example comparator 325 maybe implemented by one or more circuit(s), programmable processor(s),ASIC(s), PLD(s), FPLD(s), and/or FPGA(s), etc. When any claim of thispatent incorporating one or more of these elements is read to cover apurely software and/or firmware implementation, at least one of theexample filter 505, the example delay line 510, the example filtercoefficients 515, the example summer 518, the example coefficientadapter 520, the example subtractor 525, the example thresholder 530and/or, more generally, the example comparator 325 are hereby expresslydefined to include a tangible computer-readable medium. Example tangiblecomputer-readable media include, but are not limited to, a flash memory,a CD, a DVD, a floppy disk, a ROM, a RAM, a PROM, an EPROM, and/or anEEPROM, an optical storage disk, an optical storage device, magneticstorage disk, a magnetic storage device, and/or any other tangiblemedium that can be used to store program code and/or instructions in theform of machine-readable instructions or data structures, and which canbe accessed by a processor, a computer and/or other machine having aprocessor, such as the example processor platform P100 discussed belowin connection with FIG. 9. Combinations of the above are also includedwithin the scope of tangible computer-readable media. Further still, theexample comparator 325 may include interfaces, data structures,elements, processes and/or devices instead of, or in addition to, thoseillustrated in FIG. 5, and/or may include more than one of any or all ofthe illustrated interfaces, data structures, elements, processes and/ordevices.

FIG. 7 illustrates example machine-accessible instructions that may beexecuted to implement the example presentation verifier 205 of FIGS.2-4. FIG. 8 illustrates example machine-accessible instructions that maybe executed to implement the example metering module 245 of FIGS. 2 and3. A processor, a controller and/or any other suitable processing devicemay be used and/or programmed to execute the example machine-accessibleinstructions of FIGS. 7 and 8. For example, the machine-accessibleinstructions of FIGS. 7 and 8 may be embodied in coded instructionsstored on a tangible computer-readable medium such as a flash memory, aCD, a DVD, a floppy disk, a ROM, a RAM, a PROM, an EPROM, and/or anEEPROM, an optical storage disk, an optical storage device, magneticstorage disk, a magnetic storage device, and/or any other tangiblemedium that can be used to store program code and/or instructions in theform of machine-readable instructions or data structures, and which canbe accessed by a processor, a computer and/or other machine having aprocessor, such as the example processor platform P100 discussed belowin connection with FIG. 9. Combinations of the above are also includedwithin the scope of computer-readable media. Machine-readableinstructions comprise, for example, instructions and data that cause aprocessor, a computer and/or a machine have a processor to perform oneor more particular processes. Alternatively, some or all of the examplemachine-accessible instructions of FIGS. 7 and 8 may be implementedusing any combination(s) of ASIC(s), PLD(s), FPLD(s), FPGA(s), discretelogic, hardware, firmware, etc. Also, some or all of the exampleprocesses of FIGS. 7 and 8 may be implemented manually or as anycombination of any of the foregoing techniques, for example, anycombination of firmware, software, discrete logic and/or hardware.Further, many other methods of implementing the example operations ofFIGS. 7 and 8 may be employed. For example, the order of execution ofthe blocks may be changed, and/or one or more of the blocks describedmay be changed, eliminated, sub-divided, or combined. Additionally, anyor all of the example machine-accessible instructions of FIGS. 7 and 8may be carried out sequentially and/or carried out in parallel by, forexample, separate processing threads, processors, devices, discretelogic, circuits, etc.

The example machine-accessible instructions of FIG. 7 begin with theexample timer 335 of FIG. 3 initializing a first timer duration TIMER1(block 705). When the first timer duration TIMER1 expires (block 710),the example timer 335 initializes a second timer duration TIMER2 (block715) and enables the microphone 310 (block 717).

The example delay line 510 (FIG. 5) receives one or more samples of theaudio signal X_(c) from the STB 215 (block 720). The example filtercoefficients 515 are applied to the updated delay line 510 to form oneor more updated samples of the estimate X_(T) (block 725). The examplesubtractor 525 subtracts the updated estimates X_(T) from one or morenew samples of the audio signal X_(d) to form one or more new samples ofthe residual signal X₀ (block 730). The example coefficient adapter 520updates the filter coefficients 515 based on the new residual samplevalues X₀ (block 735).

If the second timer duration TIMER2 has not yet expired (block 740),control returns to block 720 to continue processing samples of the audiosignals X_(c) and X_(d), and updating the filter coefficients 515.

When the second timer duration TIMER expires (block 740), the examplethresholder 530 compares a magnitude of the residual signal X₀ to athreshold (block 745). As described above, based on the comparison, theexample comparator 325 sends an indication 330 representative of whetherthe media content corresponding to the audio signal X_(c) was presentedat and/or by the media presentation device 210 (block 750). The timer335 disables the microphone 310 (block 755) and control returns to block705 to wait for the timer duration TIMER1 to expire again.

The example machine-accessible instructions of FIG. 8 begin with theexample metering module 245 initializing a timer with a duration ofTIMER (block 805). When the timer expires (block 810), the meteringmodule 245 determines whether the indication 330 indicates that themedia content corresponding to the audio signal X_(c) was presented atthe media presentation device (block 815). If the indication 330indicates that the media content corresponding to the audio signal X_(c)was presented at the media presentation device (block 815), the meteringmodule 245 adds a log entry corresponding to the current media contentbeing presented (block 820). A log entry may include any desired datasuch as a timestamp, a program identifier, an audio and/or video codethat was embedded in the media signal, a signature of the media signal,a station identifier, metadata, etc. Control then returns to block 805.

If the indication 330 does not indicate that the media contentcorresponding to the audio signal X_(c) was presented at the mediapresentation device (block 815), control returns to block 805 withoutadding a log entry.

FIG. 9 is a schematic diagram of an example processor platform P100 thatmay be used and/or programmed to implement any of the example apparatusand/or methods to verify presentation of media content disclosed herein.For example, one or more general-purpose processors, processor cores,microcontrollers, etc can implement the processor platform P100.

The processor platform P100 of the example of FIG. 9 includes at leastone programmable processor P105. The processor P105 executes codedinstructions P110 and/or P112 present in main memory of the processorP105 (e.g., within a RAM P115 and/or a ROM P120). The processor P105 maybe any type of processing unit, such as a processor core, a processorand/or a microcontroller. The processor P105 may execute, among otherthings, the example machine-accessible instructions of FIGS. 7 and 8and/or, more generally, to implement the example presentation verifiers205 and the example metering modules 245 described herein.

The processor P105 is in communication with any number and/or type(s) oftangible computer-readable storage media (including a ROM P120 and/orthe RAM P115) via a bus P125. The RAM P115 may be implemented by dynamicrandom access memory (DRAM), synchronous dynamic random access memory(SDRAM), and/or any other type of RAM device, and ROM may be implementedby flash memory and/or any other desired type of memory device. Accessto the memory P115 and the memory P120 may be controlled by a memorycontroller (not shown).

The processor platform P100 also includes an interface circuit P130. Anytype of interface standard, such as an external memory interface, serialport, general-purpose input/output, etc, may implement the interfacecircuit P130. One or more input devices P135 and one or more outputdevices P140 are connected to the interface circuit P130. The inputdevices P135 may be used to implement the example microphone 310, theexample pre-amp 315 and the example ADC 320. The output devices P140 maybe used to send the indication 330 to the metering module 245 and/or theSTB 215.

Although certain example methods, apparatus, and articles of manufacturehave been described herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus, and articles of manufacture fairly falling within the scopeof the appended claims either literally or under the doctrine ofequivalents.

What is claimed is:
 1. An apparatus for use with a set-top box (STB) anda media presentation device, comprising: an audio input interface toreceive a first audio signal associated with a program selected by auser via the STB; a microphone to receive a free-field radiating secondaudio signal output by at least one of the media presentation device oran audio system associated with the media presentation device; a finiteimpulse response filter having adaptive coefficients to delay and toattenuate the first audio signal to form an estimate of the second audiosignal; a comparator to compare the second audio signal to the estimateof the second audio signal to form an output; a privacy protector tofacilitate burst mode operation of the comparator by periodicallydisabling the microphone and the comparator; and an output interface toprovide a value indicative of whether the program selected by the uservia the STB is presented at the media presentation device based on theoutput.
 2. An apparatus as defined in claim 1, further including: afirst externally-exposed connector to communicatively couple the firstaudio signal from the STB to the apparatus via a first cable; a secondexternally-exposed connector to communicatively couple the first audiosignal from the apparatus to the media presentation device via a secondcable; and a third externally-exposed connector to provide the value viaa third cable.
 3. An apparatus as defined in claim 1, further includingan audio output interface to provide the received first audio signal tothe media presentation device.
 4. An apparatus as defined in claim 1,further including a first housing to contain the audio input interface,the microphone, the comparator and the output interface, wherein thefirst housing is distinct from a second housing to contain the STB andis also distinct from a third housing to contain the media presentationdevice.
 5. An apparatus as defined in claim 1, further including a firsthousing to contain the audio input interface, the microphone, thecomparator, the output interface and the STB, and a second housing tocontain the media presentation device.
 6. An apparatus as defined inclaim 1, wherein the value indicates a first logic state when theprogram selected via the STB is output via the media presentation deviceand indicates a second logic state when the program selected via the STBis not output via the media presentation device.
 7. An apparatus asdefined in claim 1, wherein the comparator includes an echo canceller,and wherein the output of the comparator represents a magnitude of aresidual signal.
 8. An apparatus as defined in claim 1, wherein thecomparator includes a subtractor to subtract the estimate of the secondaudio signal from the second audio signal to form a residual signal. 9.An apparatus as defined in claim 8, wherein the comparator furtherincludes an adapter to adjust at least one of the adaptive coefficientsto reduce the magnitude of the residual signal.
 10. An apparatus asdefined in claim 8, wherein the comparator further includes athresholder to compare an absolute value of the residual signal to athreshold to form the output of the comparator.
 11. An apparatus asdefined in claim 1, wherein the apparatus is to be installed in-linebetween an audio output jack of the STB and an audio input jack of themedia presentation device.
 12. An apparatus as defined in claim 1,wherein the comparator selects the delay and attenuation based on amaximum coefficient magnitude of the adaptive coefficients.
 13. Anapparatus as defined in claim 1, wherein the filter is to set theadaptive coefficients to zero when the microphone is enabled.
 14. Anapparatus for use with a set-top box (STB) and a media presentationdevice comprising: an audio input interface to receive a first audiosignal associated with a program selected by a user via the STB; amicrophone to receive a free-field radiating second audio signal outputby at least one of the media presentation device or an audio systemassociated with the media presentation device; a comparator to comparethe second audio signal to the first audio signal to form an output; anoutput interface to provide a value indicative of whether the programselected by the user via the STB is presented at the media presentationdevice based on the output; and a privacy protector including a timer tofacilitate burst mode operation of the comparator by periodicallydisabling the microphone and the comparator.
 15. A method to verifypresentation at a media presentation device of media selected at atuning device, comprising: enabling a microphone to obtain a free-fieldradiating first audio signal output by the media presentation device;implementing a privacy protocol by facilitating burst mode operation ofthe microphone, the burst mode operation to periodically disable theobtaining of the first audio signal; applying a filter to a second audiosignal associated with the media received at the tuning device to forman estimate of the first audio signal by delaying and attenuating thesecond audio signal; comparing the first audio signal to the estimate ofthe first audio signal to form an output representative of whether theestimate of the first audio signal is present in the first audio signal;and providing a value indicative of whether the media received by thetuning device was presented at the media presentation device based onthe output.
 16. A method as defined in claim 15, wherein comparing thefirst audio signal to the estimate of the first audio signal includes:subtracting the estimate of the first audio signal from the first audiosignal to form a residual signal; and comparing the residual signal to athreshold.
 17. A method as defined in claim 15, wherein comparing thefirst audio signal to the estimate of the first audio signal includes:subtracting the estimate of the first audio signal from the first audiosignal to form a residual signal; updating a coefficient of the filterbased on the residual signal; computing a difference between a firstmagnitude of a first of the coefficients to a second magnitude of asecond of the coefficients; and comparing the difference to a threshold.18. A method as defined in claim 15, further including disabling thereceiving of the first audio signal after the filter has converged itsfilter coefficients.
 19. A method to verify presentation at a mediapresentation device of media selected at a tuning device, the methodcomprising: receiving a first audio signal associated with the mediareceived at the tuning device; receiving a free-field radiating secondaudio signal output by the media presentation device; implementing aprivacy protocol by: discontinuing the receiving of the second audiosignal; initializing a timer; and restarting the receiving of the secondaudio signal when the timer expires; comparing the second audio signalto an estimate of the second audio signal to form an outputrepresentative of whether the estimate of the second audio signal ispresent in the second audio signal; and providing a value indicative ofwhether the media received by the tuning device was presented at themedia presentation device based on the output.
 20. A method as definedin claim 19, wherein applying the filter to the first audio signal toform the estimate of the second audio signal includes delaying andattenuating the first audio signal.
 21. A tangible machine-readablestorage device or storage disc comprising instructions which, whenexecuted, cause a machine to at least: obtain, via a transducer,free-field radiating first audio signals output by a media presentationdevice; implement a privacy protocol by facilitating burst modeoperation of the transducer, the burst mode operation to periodicallydisable the transducer from obtaining the first audio signals; apply afilter to a second audio signal associated with media received at atuning device to form an estimate of the first audio signal, the filterto delay and to attenuate the second audio signal; compare the firstaudio signal to the estimate of the first audio signal to form an outputrepresentative of whether the estimate of the first audio signal ispresent in the second first audio signal; and provide a value indicativeof whether the media received by the tuning device was presented at themedia presentation device based on the output.
 22. A machine-readablestorage device or storage disc as defined in claim 21, wherein themachine-readable instructions, when executed, cause the machine to:subtract the estimate of the first audio signal from the first audiosignal to form a residual signal; and compare the residual signal to athreshold.
 23. A machine-readable storage device or storage disc asdefined in claim 21, wherein the machine-readable instructions, whenexecuted, cause the machine to compare the first audio signal to theestimate of the first audio signal by: subtracting the estimate of thefirst audio signal from the first audio signal to form a residualsignal; updating a coefficient of the filter based on the residualsignal; computing a difference between a first magnitude of a first ofthe coefficients to a second magnitude of a second of the coefficients;and comparing the difference to a threshold.
 24. A machine-readablestorage device or storage disc as defined in claim 21, wherein themachine-readable instructions, when executed, cause the machine toimplement the privacy protocol by: discontinuing the receiving of thefirst audio signal; initializing a timer; and restarting the receivingthe first audio signal when the timer expires.
 25. An apparatus for usewith a set-top box and a media presentation device comprising: atransducer to receive a free-field radiating first audio signal outputby the media presentation device; a filter having adaptive weights toreceive a second audio signal associated with a program selected by auser from an audio output line of the set-top box, and to process thesecond audio signal to generate a delayed and attenuated third audiosignal; a difference detector to subtract the third audio signal fromthe first audio signal to form a residual signal; a privacy protectorincluding a timer to facilitate burst mode operation by periodicallydisabling the transducer from receiving the first audio signal; and acomparator to form a value indicative of whether the program selected bythe user via the set-top box is presented at the media presentationdevice based on the residual signal.